Dendritic L-type calcium currents in mouse spinal motoneurons: implications for bistability

被引:184
作者
Carlin, KP
Jones, KE
Jiang, Z
Jordan, LM
Brownstone, RM
机构
[1] Univ Manitoba, Dept Surg, Winnipeg, MB R3E 3J7, Canada
[2] Univ Manitoba, Dept Physiol, Winnipeg, MB R3E 3J7, Canada
关键词
dihydropyridines; locomotion; plateau potential; spinal cord model;
D O I
10.1046/j.1460-9568.2000.00055.x
中图分类号
Q189 [神经科学];
学科分类号
071006 ;
摘要
The intrinsic properties of mammalian spinal motoneurons provide them with the capability to produce high rates of sustained firing in response to transient inputs (bistability). Even though it has been suggested that a persistent dendritic calcium current is responsible for the depolarizing drive underlying this firing property, such a current has not been demonstrated in these cells. In this study, calcium currents are recorded from functionally mature mouse spinal motoneurons using somatic whole-cell patch-clamp techniques. Under these conditions a component of the current demonstrated kinetics consistent with a current originating at a site spatially segregated from the soma. In response to step commands this component was seen as a late-onset, low amplitude persistent current whilst in response to depolarizing-repolarizing ramp commands a low voltage clockwise current hysteresis was recorded. Simulations using a neuromorphic motoneuron model could reproduce these currents only if a noninactivating calcium conductance was placed in the dendritic compartments. Pharmacological studies demonstrated that both the late-onset and hysteretic currents demonstrated sensitivity to both dihydropyridines and the L-channel activator FPL-64176. Furthermore, the alpha(1D) subunits of L-type calcium channels were immunohistochemically demonstrated on motoneuronal dendrites. It is concluded that there are dendritically located L-type channels in mammalian motoneurons capable of mediating a persistent depolarizing drive to the soma and which probably mediate the bistable behaviour of these cells.
引用
收藏
页码:1635 / 1646
页数:12
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